1. Field
The present disclosure relates to technology for wireless communication systems, such as, but not limited to, satellite communication systems.
2. Description of the Related Art
A satellite communication system includes one or more satellites, one or more satellite terminals, hereafter sometimes simply called terminals, and one or more network nodes which may provide satellite network connectivity, system services, management, control, and/or external interface functions. A satellite terminal can, e.g., provide connectivity with one or more satellites in order to provide satellite system data, control and/or management plane services. Additionally, or alternatively, a satellite terminal may provide connectivity to other network nodes in the satellite communication system that supports these services. Satellite terminals may be ground-based, airborne, marine-based, or space-based. In some cases, the satellite terminal can be located on the satellite, but unless specified, is presumed to be remote from the satellite. A satellite communication system typically includes satellite terminals that can communicate with one another utilizing at least one of the satellites. The satellite terminals may also utilize zero, one or more satellites and zero, one or more other satellite terminals to wirelessly obtain access to other networks. For example, a satellite terminal may utilize a satellite and another satellite terminal (e.g., a gateway type of satellite terminal) to wirelessly connect to the Internet, and thereby, obtain any type of information that is readily available over the Internet.
A satellite communication system is typically assigned one or more specific radio frequency (RF) and/or optical bands that the satellite communication system is allowed to use to provide its communication capabilities to its satellite terminals. Other types of wireless communication systems, such as a ground-based communication system, are each assigned their own RF and/or optical bands, which are typically different than those used by a satellite communication system. This way, at least theoretically, a satellite communication system and another communication system will not interfere with one another. In other words, a satellite communication system should preferably not produce interference that adversely affects another communication system, and vice versa.
Interference can adversely affect a satellite communication system. Costs associated with interference mitigation and loss of revenue may exceed multiple millions of dollars per year for a satellite communication system. Such costs can include lost or reduced revenues due to delays of the start of services. Additionally, because of interference, transponders may be directed to operate in a backed off mode that results in less power and/or bandwidth available for use or sale.
There are various types of interference that may adversely affect a satellite communication system, such as, but not limited to, user error, cross-polarization leakage, adjacent satellites, terrestrial services and deliberate interference. User interference can result, e.g., from an operator error, equipment malfunction, poor cable shielding, and the like. Cross-polarization leakage, which can also be called cross-polarization interference, may be caused by incompatible modulation types (such as FM TV) transmitted in an opposite polarization field, poorly aligned antennas and/or inexperience of uplink operators. Adjacent satellite interference, which may be caused by operator error or poor inter-system coordination, has become more prevalent as smaller spacing between frequency bands assigned to different satellite communication systems becomes more common. Terrestrial interference may be caused by terrestrial microwave systems as well as by radar systems, but are not limited thereto. Deliberate interference can be caused by radio jamming equipment, or the like.
Over the relatively long term, interferers may be identified and then modified or shut down as appropriate, if possible. However, in the relatively short term, a satellite communication system may adapt to interference only after a satellite terminal of the satellite communication system has dropped a link or has informed a subsystem of the satellite communication system (which is responsible for dynamic resource allocation (DRA) and/or dynamic link adaption) of their poor link quality. In other words, a satellite communication system typically deals with interference in a reactive manner.
Mobile satellite terminals, which can also be referred to as mobile communication terminals or more succinctly as mobile terminals, often rely on a wireless communication system (e.g., a satellite and/or a ground-based communication system) to obtain navigational route information used for directing the mobile terminals from their present locations to target locations. Such mobile terminals can be, e.g., mobile telephones, mobile multi-media devices or navigational subsystems of manned, autonomous or semi-autonomous vehicles. A manned, autonomous, or semi-autonomous vehicle can be, for example, an aircraft, a car, a truck, a train, a bus or a boat. Where an autonomous or semi-autonomous vehicle is an aircraft, it can also be referred to as a drone. Many vehicles include a navigational subsystem that relies on global positioning system (GPS) satellites to track a present location of the vehicle, which is used by software to determine and provide directions to a human driver or to a computer that controls an autonomous or semi-autonomous vehicle. Some navigational subsystems allow a driver to select from among different routes that have different characteristics, such as, but not limited to, a shortest distance route, a shortest travel time route, a least amount of highway travel route, and a most amount of highway travel route. When following one of the routes specified by the navigational subsystem, a mobile terminal can potentially lose one or more communication capabilities. In other words, a mobile terminal may lose a communication capability while travelling between a present location of the mobile terminal and a target destination for the mobile terminal. Exemplary types of communication capabilities that may be lost, at least temporarily, include a GPS or other navigation capability, a control and/or status link, a voice telephony capability, and a multimedia communications capability. When a GPS navigation capability is lost, the user terminal may at least temporarily be unable to determine its location and/or provide directions. This may be frustrating to a driver that was following directions provided by the navigational subsystem type of mobile terminal. This may be catastrophic to an autonomous navigational subsystem type of mobile terminal.
Autonomous or semi-autonomous vehicles can utilize navigational subsystems to autonomously or semi-autonomously transport people and/or cargo from one location to another. Autonomous or semi-autonomous vehicles (e.g., drones) can alternatively utilize navigational subsystems to perform surveillance, e.g., in hostile territories. Alternatively, or additionally, autonomous or semi-autonomous vehicles can utilize navigational subsystems to carry a communication payload. For example, drones that carry a communication payload may be directed to fly over specific geographic regions at specific times to add communication capabilities to areas that would otherwise not be satisfactorily serviced, e.g., because of high traffic demands or communication dead zones. Another example of an autonomous or semi-autonomous vehicle is a rover that explores the moon or another planet, such as Mars.